(a) Field of the Invention
The present invention relates to a liquid crystal display and a substrate thereof, and more particularly, to a vertically aligned liquid crystal display and a substrate thereof in which pixel regions are divided into a plurality of small domains to obtain a wide viewing angle.
(b) Description of the Related Art
In a liquid crystal display (LCD), liquid crystal material is injected between an upper substrate, on which common electrodes and a color filter are formed, and a lower substrate, on which thin film transistors and pixel electrodes are formed. A voltage of a different potential is applied to the pixel electrodes and common electrodes to form an electric field, thereby varying the alignment of liquid crystal molecules of the liquid crystal material. In this way, the transmittance of incident light is controlled to enable the display of images.
However, a serious drawback of LCDs is their limited viewing angle. Various methods and configurations have been developed in an attempt to overcome this problem. In one method, the liquid crystal molecules are aligned perpendicularly to the upper and lower substrates, and either a predetermined aperture pattern or protrusions are formed on the pixel electrodes and the opposing common electrodes.
By forming the aperture patterns on the pixel electrodes and common electrodes, a fringe field is generated. Using the fringe field, a slanting direction of the liquid crystal molecules is controlled such that the viewing angle is increased. When there are formed protrusions on the pixel electrodes and common electrodes, on the other hand, an electric field distorted by the protrusions is used to control the slanting direction of the liquid crystal molecules. In an alternative method, aperture patterns are formed in the pixel electrodes provided on the lower substrate and protrusions are formed on the common electrodes provided on the upper substrate. Using a fringe field generated by the aperture pattern and protrusions, the slanting direction of the liquid crystal molecules is controlled to form domains.
However, in the above methods, dark portions where light is not transmitted appear in areas where the aperture patterns and protrusions are formed. As a result, if an area occupied by the aperture patterns and protrusions is excessively large, brightness is reduced. If the number of aperture patterns and protrusions is reduced in an attempt to remedy this problem, the ability to control the slanting of the liquid crystal molecules is reduced such than an uneven alignment results. Hence, texture is generated and extends over relatively large areas so that brightness is negatively affected, degrading overall picture quality.